The sound barrier

A cone of water vapor surrounds an F/A-18F Super Hornet airplane as it approaches the sound barrier during the New York Air Show at Jones Beach State Park.

Rings like this can form as an aircraft traveling low over the water nears the speed of sound. Pressure created by sound waves squeezes moisture from the air, creating the "artificial cloud."

Pilot whales

May 30, 2009--Rescuers try to push one of about 55 pilot whales that mysteriously stranded themselves back to sea.

Though more than 20 of the mammals survived, the rest were euthanized by gunshots to the head, BBC News reported.

Dead Animals

im Patton walks to a cabinet and pulls open a drawer. Out slide two neat rows of chipmunks, impeccably preserved. Officious handwritten tags tell the story of each and every animal’s capture. In a screwtop container on the tray, a half-dozen chipmunk skulls rattle, picked clean of all their tissue by a beetle colony housed downstairs

Patton is director emeritus of UC Berkeley’s Museum of Vertebrate Zoology, and he clearly relishes guiding people through the bewilderingly and impressive collection. The MVZ is a premiere research institution with a broad, deep set of well-preserved specimens ranging from tiny shrews to huge bears.But, don’t pack your bags for California just yet, though, the MVZ is not open to the public.

But this video is the next best thing. Wired Science takes you on a behind-the-scenes tour of this amazing instituion. You’ll visit the bone room and the fur room, where the big mammals are kept. You’ll see capybara furs, komodo dragon skins, and whale skulls.

We were more than content to just stare at the wonder of biodiversity, but scientists use the specimens to provide baselines for environmental contamination by testing the amount of lead, say, in a wolverine’s skin. By comparing it with modern samples, they can determine how much humans have mucked up the biosphere.

They can even extract genetic material and analyze how ecological change has affected the genetic diversity of many types of mammals. Of course, when some of the specimens were collected, the technology necessary to do those experiments wasn’t even on the horizon. With that in mind, Patton and his team tried to future-proof the new specimens they bring into the museum.

“One of the goals of maintaining a collection like this is to maintain as much as you can,” Patton said, “not just for the purpose that it can be used today but trying to anticipate what purposes it might be used for as techniques become available in the future.”

Undersea Volcanic Eruptions

A crack team of "rapid response" volcano experts scrambled to the South Pacific Ocean last month to find something rarely seen by human eyes: an underwater eruption exploding into the inky, cold depths and spewing lava onto the ocean floor.

The realm of underwater volcanic eruptions is a strange, uncharted one. As much as 80 percent of the planet's volcanic activity is thought to occur on the sea floor, but scientists are rarely able to witness the events.

One of the few other undersea volcanoes recorded by researchers was when a series of eruptions near the island of Guam in 2004 vented droplets of liquid carbon dioxide and formed pools of liquid sulfur.

Last November, a team led by Joseph Resing of the National Oceanic and Atmospheric Administration's Pacific Marine Environmental Laboratory in Seattle detected a plume of volcanic material floating in the water column, above the Lau Basin, 140 miles southwest of Samoa. On May 6 they returned and sent the remotely operated vehicle (ROV) Jason-2 into the abyss, wondering if the fiery theater was still going.

It was. The team saw glowing, red-hot lava creeping out of a vent called Hades on the West Mata volcano, nearly 4,000 feet under water. Ocean water chills lava on contact, forming pillow-shaped rocks that are commonly found on land, but that no one had ever witnessed growing on the ocean floor. About 100 meters (328 feet) from Hades, another vent, Prometheus, flung chunks of lava into the ocean. Though the water's crushing pressure damped the explosion, bursts of gas pushed ash and rocks 20 meters (66 feet) above the vent. Jason-2 swam near the vent to take readings and was promptly buried in 100 pounds of debris.

"The degassing is pretty spectacular," William Chadwick of Oregon State University, who was not involved in the cruise, said. "There's been a long debate about how explosions look at depth, and you have these huge gas bubbles, maybe one meter (3.28 feet) across, coming out of West Mata."

Just 40 kilometers (25 miles) away, the team found the remnants of yet another eruption, this one at a mid-ocean ridge called the Lau Basin spreading center. The lavas were fresh, indicating the basin erupted at roughly same time as West Mata, but had stopped since November.

The team also observed a species of shrimp living on the volcano. It's the only living thing daring enough to eke out an existence in the hellish scene, but Robert Embley of the National Oceanic and Atmospheric Administration's Pacific Marine Environmental Laboratory said they found them near Guam in 2004, too.

"The real story might be in how unique they are," he said. "How many other places do these shrimp exist? Are they unique to erupting volcanoes? We don't know yet, but that'd be pretty interesting."

How to Clean a Skull

If you want to save a biological specimen for science, you can’t just toss it a cabinet. There’s a science to preservation and nowhere practices it better than at the University of California, Berkeley’s Museum of Vertebrate Zoology.
Wired Science News for Your Neurons
Video: How to Clean a Skull (Hint: Flesh-Eating Beetles)

* By Alexis Madrigal Email Author
* June 8, 2009 |
* 12:00 am |
* Categories: Animals, Video Podcast

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BERKELEY, California — If you want to save a biological specimen for science, you can’t just toss it a cabinet. There’s a science to preservation and nowhere practices it better than at the University of California, Berkeley’s Museum of Vertebrate Zoology.

Housing hundreds of thousands of specimens, the museum has been at the forefront of preservation techniques since it was founded in 1908. For example, the MVZ pioneered the technique of using flesh-eating beetles to clean the skeletons of small mammals. Depending on how hungry the beetles are, it can take as little as 24 hours for them to strip the meat from the skull of a small mammal.

In this video (which is safe for work but probably not for the squeamish), we take you on a step-by-step tour of the preservation process.

“If you’re going to kill something, you want to maximize the potential use of it, not just for today, but forever,” said Jim Patton, the director emeritus of the museum.

The MVZ isn’t open to the public, but Wired Science toured its hallowed vaults to give you a peek inside a working zoology research facility. In Part 1 of this video series, we present the bone and fur rooms, which store large mammal parts. In the third video, we will look into the significance of the collection and how it has been used as a massive dataset for observing climate change.

Machu Picchu Described as Pilgrimage Site

Machu Picchu, the "lost city of the Incas," was not a true city but rather a pilgrimage center symbolically connected to the Andean vision of the cosmos, an Italian study has concluded.

According to Giulio Magli, professor of archaeoastronomy at Milan's Polytechnic University, Machu Picchu was the ideal counterpart of the Island of Sun, a rocky islet in the southern part of Lake Titicaca.

"This island had a very important sanctuary which was a destination of pilgrimage. An apparently insignificant rock was believed to be the place of birth of the sun, and therefore of the Inca civilization," Magli told Discovery News.

The Inca, who ruled the largest empire on Earth by the time their last emperor, Atahualpa, was garroted by Spanish conquistadors in 1533, believed that the sun god was their ancestor.

Surrounded on three sides by the gorges of the Urubamba River (also called the Vilcanota River), and tucked between two massive mountain peaks -- the Huayna Picchu and the Machu Picchu -- the Inca city features about 200 stone structures and was probably inhabited by no more than 750 people. It is perched some 8,000 feet in the clouds.After its abandonment at the time of the Spanish conquest, it was lost to the jungle for nearly 500 years, and was then discovered by Hiram Bingham, an American explorer, in 1911 (although recent studies claim that it was actually discovered 40 years earlier by an obscure German entrepreneur).

Theories about the city's function abound. Machu Picchu has been wrongly identified as the traditional birthplace of the Inca people, their final stronghold, and a sacred center occupied by virgins devoted to the sun god.

Another recent interpretation, based on archival research published in the mid-1980s, and widely supported by scholars, suggests the spectacular site was a private estate of the emperor Pachacuti, who built it around 1460 A.D.

"Any interpretation is doomed to remain speculative. Machu Picchu remains a mystery. We do not know for sure what the Inca called it, we do not know when and why it was constructed, or why it was abandoned," Magli said.

Published on the Cornell University physics Web site arXiv.org, Magli's study examined Machu Picchu's urban layout, its ancient access ways, and the position of the site in relation with the cycles of celestial bodies during the Inca's reign. He then compared these aspects to a well-documented Inca pilgrimage site on Lake Titicaca, located on the border of Bolivia and Peru . According to Magli, the pilgrimage to Machu Picchu avoided a much easier and faster route along the Urubamba River, instead ascending through the difficult and spectacular Inca trail, which ended at the gate of the town.

"The admitted visitors perhaps left their ritual offerings just near the entrance wall. Indeed, many peculiar stone pebbles, mainly of obsidian, have been recovered there," Magli said.

"The pilgrims were then confronted by the imposing view of the Huayna Picchu mountain. Most likely, this was their final destination. Indeed, the last part of the pilgrimage, oriented north, took place inside the town," Magli said.

The author of "Mysteries and Discoveries of Archaeoastronomy," Magli suggests that the ceremonial path into the city was conceived as a replica of the path followed by the first Incas in cosmological myth.

In their final leg, the pilgrims approached three important places: the so-called quarry, an area possibly connected with Mother Earth and the underground travel of the first Incas, the temple of the three windows (it was believed that the first Incas came out from one of the three windows), and the Intihuatana Pyramid, which resembled the sacred mountain Huayna Picchu, located at the end of the path.

According to Magli, the picture also fits with celestial cycles that appeared in the sky at the times of the Incas. These were dominated by the Milky Way, which was perceived as a "celestial river" having its terrestrial counterpart in the Urubamba River.

"Machu Picchu was located at the ideal, opposite crossroads between the terrestrial and the celestial rivers. It was the other end of the sun's path," Magli concluded.

According to Jean-Pierre Protzen, who teaches architecture at the University of California, Berkeley, the study brings an additional dimension to the site.

"Magli's argument that Machu Picchu was a pilgrimage site and not a royal estate is well worth considering, although it is in need of a much more substantial proof. There is no reason to believe that it could not have been both," Protzen, a leading expert on Inca architecture.

Halo Lopped Off

A halo of stars surrounding a galaxy in the relatively nearby Virgo cluster is missing, possibly torn away by a neighboring galaxy or snuffed out by the collapse of the cluster itself.

The victim is the giant elliptical galaxy Messier 87, which lives about 50 million light-years away in the center of the Virgo, the closest galaxy cluster to Earth.

"We were surprised to see that the star in the galactic halo in M87 stopped after a certain radius in the center," Ortwin Gerhard, a researcher with Germany's Max Planck Institute for Extraterrestrial Physics, told Discovery News.

Astronomers were looking at planetary nebula, the exploded remains of stars, using a light-splitting spectrograph at the European Southern Observatory's Very Large Telescope in Chile when they made their discovery.

"It was more like an accident," said Gerhard, co-author of paper scheduled to be published in the journal Astronomy and Astrophysics. "We were studying the Virgo cluster trying to find stars that do not belong to galaxies, but lie between them."Planetary nebulas are shells of gas illuminated by the energy of stellar core explosions. In M87's case, they are bright enough to be seen as individual points of light, though the measurements are time-consuming and painstaking.

Astronomers in Europe and the United States partnered to first find planetary nebulas in the Virgo Cluster and then determine their speeds using an instrument called FLAMES, which can make simultaneous measurements of light sources over an area of the sky about the size of the moon.

"Planetary nebulas are dying stars," said John Feldmeier, an astronomer at Youngstown State University in Ohio. "We like them because they're very common. They act like tracers for the other stars that are there but too hard to observe."

Folding the data into computer models, scientists realized that M87's gravitational reach extended about one-third as far as predicted and few clues to explain why.If M87's outer edge was stripped away by the cluster or another galaxy, straggler stars should still be visible.

"We don't see them and we should be able to because they don't move so fast," Gerhard said. "Either it would have had to happen a long time ago so that the stars would have had time to disappear or they were never there."

Perhaps M87 star formation was cut short by the galaxy cluster collapsing, or perhaps its small feeder galaxies were not able to support stellar nurseries, Gerhard added.

"We really don't understand how galaxies form and change over time," said Feldmeier.

The scientists plan follow-up studies to try to refine M87's boundaries even further.

Fake Astronaut Gets Hit by Artificial Solar Flare

In 1972, Apollo astronauts narrowly escaped a potential catastrophe. On August 2nd of that year, a large and angry sunspot appeared and began to erupt, over and over again for more than a week, producing a record-setting fusillade of solar proton radiation. Only pure luck saved the day. The eruptions took place during the gap between Apollo 16 and 17 missions, so astronauts missed the storm.

Still wonder, what would have happened if the timing had been just a little different, what if astronauts had been caught unprotected on the surface of the Moon?

NASA needs to know. The agency is in high gear preparing to send people to the Moon to set up a manned outpost, a step toward eventually sending humans to Mars or elsewhere in the solar system. These missions will take astronauts outside the protection of Earth's magnetic field for months or even years at a time, and NASA must know how to keep its explorers safe from extreme solar storms.

So scientists are creating an artificial solar radiation storm right here on Earth. And they're testing its effects on an artificial human: Matroshka, the Phantom Torso.The European Space Agency's Matroshka and his NASA counterpart Fred have already flown in experiments aboard the Space Shuttle and the International Space Station that have shown how other kinds of space radiation such as cosmic rays penetrate the human body. Now, scientists at Brookhaven National Laboratory in Upton, New York, are subjecting an artificial torso to a beam of protons to learn how astronauts would be affected by the 1972 event.

"We want to know how close it comes to a dangerously acute exposure," says Francis Cucinotta, the Chief Scientist for NASA's Radiation Program at the Johnson Space Center in Houston, Texas.

In the parlance of radiation experts, "acute exposure" is brief but intense. Radiation strikes the body over a relatively short period of time ranging from minutes to hours—just like a solar flare. This is different from the "chronic exposure" astronauts normally experience as they travel through space. Cosmic rays hit their bodies in a slow drizzle spread out over weeks or months. With chronic exposure, the body has time to repair or replace damaged cells as it goes along, but an acute exposure gives the body little time to cope with the damage.


The radiation beamline at NASA's Space radiation Lab in Brookhaven.

"The biological effects are very sensitive to the dose rate," Cucinotta explains. "A dose of radiation delivered over a short amount of time is two to three times more damaging than the same dose over a few days."

At first glance, the 1972 event would seem to fall into the acute category—it was after all a solar flare. But there's a problem. It was actually a series of flares producing a radiation storm that was longer and less impulsive than normal. Radiation exposure would have been neither chronic nor clearly acute, but somewhere in between. In this gray area, details about how much of the radiation actually reaches a person’s vital organs — versus how much is blocked by their spacesuit, skin and muscles — can make all the difference.

Matroshka is helping scientists understand these details. He's a life-size plastic replica of a human torso, sans arms and legs. The plastic closely matches the density of organs and tissues in the human body, and this Phantom Torso is embedded with hundreds of radiation sensors throughout his body. He even has real human blood cells."We put blood cells in small tubes in the stomach and in some places in the bone marrow," some of which are deep within the torso while others are close to the surface where there's less "tissue" to block radiation. "One of the questions we have is whether the less shielded parts of the bone marrow will be [much harder hit]," raising the risks of leukemia and other cancers.

Using real blood cells lets scientists see how much the radiation damages the cells' DNA. High-speed particles of proton radiation can smash into DNA, breaking the string-like molecules. Cells can usually repair these breaks, but if several breaks occur within a short period of time, the damage can be irreparable. At best, the cell will then self-destruct. At worst, it will go haywire and grow out of control, becoming cancerous.

To subject Matroshka to a 1972-style radiation storm, scientists have devised a way to simulate that event using a high-energy proton beam at NASA's Space Radiation Lab in Brookhaven. The beam fans out so that, at the point where Matroshka sits, it's 60 cm across — large enough to engulf the entire torso. By stepping the energy of the beam through a series of energy levels, scientists can mimic the unique energy spectrum of the protons in the 1972 event.

In the upcoming experiment, led by Guenther Reitz of the German Aerospace Center (DLR) in Cologne, Matroshka's radiation sensors will reveal how much proton radiation reaches various parts of the mannequin's body. "With protons, you might have an order of magnitude (a factor of ten) difference from one part of the body to another," notes Cucinotta.

The readings will help mission planners figure out how much shielding is necessary to protect real astronauts from a 72-style storm. The results will also point researchers in the right direction for medical treatments that might help mitigate the effects of such an event.

Unlike a real astronaut, Matroshka can withstand multiple flares with no lasting side effects. A quick transfusion of blood cells and voilà--Matroshka is ready for another blast

The readings will help mission planners figure out how much shielding is necessary to protect real astronauts from a 72-style storm. The results will also point researchers in the right direction for medical treatments that might help mitigate the effects of such an event.

Unlike a real astronaut, Matroshka can withstand multiple flares with no lasting side effects. A quick transfusion of blood cells and voilà--Matroshka is ready for another blast.

So let the flares begin—and stay tuned for results.
Author: Dr. Tony Phillips | Credit: Science@NASA

Computer Graphics Researchers Simulate The Sounds Of Water And Other Liquids

The sounds produced by pouring and splashing water actually result from the vibration of trapped air bubbles. Cornell researchers can simulate those sounds by computing how the bubbles would behave. (Credit: Doug James)
Splash, splatter, babble, sploosh, drip, drop, bloop and ploop!
Those are some of the sounds that have been missing from computer graphic simulations of water and other fluids, according to researchers in Cornell's Department of Computer Science, who have come up with new algorithms to simulate such sounds to go with the images.

The work by Doug James, associate professor of computer science, and graduate student Changxi Zheng will be reported at the 2009 ACM SIGGRAPH conference Aug. 3-7 in New Orleans. It is the first step in a broader research program on sound synthesis supported by a $1.2 million grant from the Human Centered Computing Program of the National Science Foundation (NSF) to James, assistant professor Kavita Bala and associate professor Steve Marschner.

In computer-animated movies, sound can be added after the fact from recordings or by Foley artists. But as virtual worlds grow increasingly interactive and immersive, the researchers point out, sounds will need to be generated automatically to fit events that can't be predicted in advance. Recordings can be cued in, but can be repetitive and not always well matched to what's happening.

"We have no way to efficiently compute the sounds of water splashing, paper crumpling, hands clapping, wind in trees or a wine glass dropped onto the floor," the researchers said in their research proposal.

Along with fluid sounds, the research also will simulate sounds made by objects in contact, like a bin of Legos; the noisy vibrations of thin shells, like trash cans or cymbals; and the sounds of brittle fracture, like breaking glass and the clattering of the resulting debris.

All the simulations will be based on the physics of the objects being simulated in computer graphics, calculating how those objects would vibrate if they actually existed, and how those vibrations would produce acoustic waves in the air. Physics-based simulations also can be used in design, just as visual simulation is now, James said. "You can tell what it's going to sound like before you build it," he explained, noting that a lot of effort often goes into making things quieter.

In their SIGGRAPH paper, Zheng and James report that most of the sounds of water are created by tiny air bubbles that form as water pours and splashes. Moving water traps air bubbles on the scale of a millimeter or so. Surface tension contracts the bubbles, compressing the air inside until it pushes back and expands the bubble. The repeated expansion and contraction over milliseconds generates vibrations in the water that eventually make its surface vibrate, acting like a loudspeaker to create sound waves in the air.

The simulation method developed by the Cornell researchers starts with the geometry of the scene, figures out where the bubbles would be and how they're moving, computes the expected vibrations and finally the sounds they would produce. The simulation is done on a highly parallel computer, with each processor computing the effects of multiple bubbles. The researchers have fine-tuned the results by comparing their simulations with real water sounds.

Demonstration videos of simulations of falling, pouring, splashing and babbling water are available at http://www.cs.cornell.edu/projects/HarmonicFluids.

The current methods still require hours of offline computing time, and work best on compact sound sources, the researchers noted, but they said further development should make possible the real-time performance needed for interactive virtual environments and deal with larger sound sources such as swimming pools or perhaps even Niagara Falls. They also plan to approach the more complex collections of bubbles in foam or plumes.

The research reported in the SIGGRAPH paper was supported in part by an NSF Faculty Early Career Award to James, and by the Alfred P. Sloan Foundation, Pixar, Intel and Autodesk.

Scientists Create Metal That Pumps Liquid Uphill

A piece of metal altered by Chunlei Guo's ultra-powerful laser pulls liquid uphill. (Credit: Image courtesy of University of Rochester)

In nature, trees pull vast amounts of water from their roots up to their leaves hundreds of feet above the ground through capillary action, but now scientists at the University of Rochester have created a simple slab of metal that lifts liquid using the same principle—but does so at a speed that would make nature envious.
The metal, revealed in an upcoming issue of Applied Physics Letters, may prove invaluable in pumping microscopic amounts of liquid around a medical diagnostic chip, cooling a computer's processor, or turning almost any simple metal into an anti-bacterial surface.

"We're able to change the surface structure of almost any piece of metal so that we can control how liquid responds to it," says Chunlei Guo, associate professor of optics at the University of Rochester. "We can even control the direction in which the liquid flows, or whether liquid flows at all."

Guo and his assistant, Anatoliy Vorobyev, use an ultra-fast burst of laser light to change the surface of a metal, forming nanoscale and microscale pits, globules, and strands across the metal's surface. The laser, called a femtosecond laser, produces pulses lasting only a few quadrillionths of a second—a femtosecond is to a second what a second is to about 32 million years. During its brief burst, Guo's laser unleashes as much power as the entire electric grid of North America does, all focused onto a spot the size of a needlepoint, he says.

The wicking process, which on Guo's metal moves at a quick one centimeter per second speed against gravity, is very similar to the phenomenon that pulls spilled milk into a paper towel or creates "tears of wine" in a wineglass—molecular attractions and evaporation combine to move a liquid against gravity, says Guo. Likewise, Guo's nanostructures change the way molecules of a liquid interact with the molecules of the metal, allowing them to become more or less attracted to each other, depending on Guo's settings. At a certain size, the metal nanostructures adhere more readily to the liquid's molecules than the liquid's molecules adhere to each other, causing the liquid to quickly spread out across the metal. Combined with the effects of evaporation as the liquid spreads, this molecular interaction creates the fast wicking effect in Guo's metals.

Adding laser-etched channels into the metal further enhances Guo's control of the liquid.

"Imagine a huge waterway system shrunk down onto a tiny chip, like the electronic circuit printed on a microprocessor, so we can perform chemical or biological work with a tiny bit of liquid," says Guo. "Blood could precisely travel along a certain path to a sensor for disease diagnostics. With such a tiny system, a nurse wouldn't need to draw a whole tube of blood for a test. A scratch on the skin might contain more than enough cells for a micro-analysis."

Guo's team has also created metal that reduces the attraction between water molecules and metal molecules, a phenomenon called hydrophobia. Since germs mostly consist of water, it's all but impossible for them to grow on a hydrophobic surface, says Guo.

Currently, to alter an area of metal the size of a quarter takes 30 minutes or more, but Guo and Vorobyev are working on refining the technique to make it faster. Fortunately, despite the incredible intensity involved, the femtosecond laser can be powered by a simple wall outlet, meaning that when the process is refined, implementing it should be relatively simple.

Guo is also announcing this month in Physical Review Letters a femtosecond laser processing technique that can create incandescent light bulbs that use half as much energy, yet produce the same amount of light. In 2006, Guo's team used the femtosecond laser to create metal with nanostructures that reflected almost no light at all, and in 2008 the team was able to tune the creation of nanostructures to reflect certain wavelengths of light—in effect turning almost any metal into almost any color.

This research funded by the U.S. Air Force Office of Scientific Research and the National Science Foundation.

Electronic Memory Chips That Can Bend And Twist

Electronic memory chips may soon gain the ability to bend and twist like this one. (Credit: NIST)

Electronic memory chips may soon gain the ability to bend and twist as a result of work by engineers at the National Institute of Standards and Technology (NIST). As reported in the July 2009 issue of IEEE Electron Device Letters, the engineers have found a way to build a flexible memory component out of inexpensive, readily available materials.
Though not yet ready for the marketplace, the new device is promising not only because of its potential applications in medicine and other fields, but because it also appears to possess the characteristics of a memristor, a fundamentally new component for electronic circuits that industry scientists developed in 2008. NIST has filed for a patent on the flexible memory device (application #12/341.059).

Electronic components that can flex without breaking are coveted by portable device manufacturers for many reasons—and not just because people have a tendency to drop their mp3 players. Small medical sensors that can be worn on the skin to monitor vital signs such as heart rate or blood sugar could benefit patients with conditions that require constant maintenance, for example. Though some flexible components exist, creating flexible memory has been a technical barrier, according to NIST researchers.

Hunting for a solution, the researchers took polymer sheets—the sort that transparencies for overhead projectors are made from—and experimented with depositing a thin film of titanium dioxide, an ingredient in sunscreen, on their surfaces. Instead of using expensive equipment to deposit the titanium dioxide as is traditionally done, the material was deposited by a sol gel process, which consists of spinning the material in liquid form and letting it set, like making gelatin. By adding electrical contacts, the team created a flexible memory switch that operates on less than 10 volts, maintains its memory when power is lost, and still functions after being flexed more than 4,000 times.

What's more, the switch's performance bears a strong resemblance to that of a memristor, a component theorized in 1971 as a fourth fundamental circuit element (along with the capacitor, resistor and inductor). A memristor is, in essence, a resistor that changes its resistance depending on the amount of current that is sent through it—and retains this resistance even after the power is turned off. Industrial scientists announced they had created a memristor last year, and the NIST component demonstrates similar electrical behavior, but is also flexible. Now that the team has successfully fabricated a memristor, NIST can begin to explore the metrology that may be necessary to study the device's unique electrical behavior.

"We wanted to make a flexible memory component that would advance the development and metrology of flexible electronics, while being economical enough for widespread use," says NIST researcher Nadine Gergel-Hackett. "Because the active component of our device can be fabricated from a liquid, there is the potential that in the future we can print the entire memory device as simply and inexpensively as we now print a slide on an overhead transparency."

Secret Of Sandcastle Construction Could Help Revive Ancient Building Technique

The monastery in Kagbeni, in the Buddhist kingdom of Mustang, Nepal. The monastery was established in 1429. (Credit: Copyright Paul Jaquin/Durham University)

The secret of a successful sandcastle could aid the revival of an ancient eco-friendly building technique, according to research led by Durham University.
Researchers, led by experts at Durham's School of Engineering, have carried out a study into the strength of rammed earth, which is growing in popularity as a sustainable building method.

Just as a sandcastle needs a little water to stand up, the Durham engineers found that the strength of rammed earth was heavily dependent on its water content.

Rammed earth is a manufactured material made up of sand, gravel and clay which is moistened and then compacted between forms to build walls. Sometimes stabilisers such as cement are added but the Durham research focussed on unstabilised materials.

The research, funded by the Engineering and Physical Sciences Research Council (EPSRC) and published in the journal Geotechnique, showed that a major component of the strength of rammed earth was due to the small amount of water present.

Small cylindrical samples of rammed earth underwent "triaxial testing" – where external pressures are applied to model behaviour of the material in a wall. The researchers found that the suction created between soil particles at very low water contents was a source of strength in unstabilised rammed earth.

They showed that rammed earth walls left to dry after construction, in a suitable climate, could be expected to dry but not lose all their water. The small amount of water remaining provided considerable strength over time.

The researchers say their work could have implications for the future design of buildings using rammed earth as the link between strength and water content becomes clearer.

There is increasing interest in using the technique as it may help reduce reliance on cement in building materials (cement production being responsible for five per cent of man's CO2 output (1)). Rammed earth materials can usually also be sourced locally, thereby reducing transport needs.

As well as informing new build designs the team hopes their findings could also aid the conservation of ancient rammed earth buildings by putting methods in place to protect against too much water entering a structure, which would reduce its strength. Paul Jaquin, a researcher on the project is now working for an engineering consultancy (Ramboll, UK) on new earth building projects around the world, using this research to better engineer buildings.

Research project leader, Dr Charles Augarde, of Durham University's School of Engineering, said: "We know that rammed earth can stand the test of time but the source of its strength has not been understood properly to date.

"Without this understanding we cannot effectively conserve old rammed earth or make economic designs for new build.

"Our initial tests point to its main source of strength being linked to its water content.

"By understanding more about this we can begin to look at the implications for using rammed earth as a green material in the design of new buildings and in the conservation of ancient buildings that were constructed using the technique."

Rammed earth was developed in ancient China around 2,000 years before Christ, when people used the technique to build walls around their settlements and the technique spread throughout the world - as documented in another recent publication by the researchers linking up with Dr Chris Gerrard, of the Department of Archaeology, at Durham University (*).

Parts of the Great Wall of China and the Alhambra at Granada in Spain were built using rammed earth.

In the UK the technique was used to build experimental low cost housing, in Amesbury, Wiltshire, following the end of the First World War, and it is a recognised building method in parts of Australia and the USA.

The popularity of eco-friendly homes showcased on television programmes such as Grand Designs has also brought the technique to people's attention.

Dr Augarde is a co-director of Earth Building UK (EBUK), a new association established this year to foster the conservation, understanding and development of building with earth in the United Kingdom.

EBUK brings together builders, academics, researchers, architects, engineers, manufacturers and many more to work in areas of common interest at a national and local level.

Tom Morton, Secretary of Earth Building UK, said: "This kind of research is very valuable as the construction industry analyses environmentally sound, traditional ways of building and adapts them for sustainable construction in the 21st century.

"Such low-carbon technologies are most likely to succeed by marrying the expertise of our research universities, such as Durham, with the commercial understanding of the wider industry and we are seeing a number of very exciting developments in this area.

Saturn's Moon Titan: Cassini Finds Titan's Clouds Hang On To Summer

ScienceDaily (June 4, 2009) — Cloud chasers studying Saturn's moon Titan say its clouds form and move much like those on Earth, but in a much slower, more lingering fashion.

Their forecast for Titan's early autumn -- warm and wetter.

Scientists with NASA's Cassini mission have monitored Titan's atmosphere for three-and-a-half years, between July 2004 and December 2007, and observed more than 200 clouds. They found that the way these clouds are distributed around Titan matches scientists' global circulation models. The only exception is timing -- clouds are still noticeable in the southern hemisphere while fall is approaching.

"Titan's clouds don't move with the seasons exactly as we expected," said Sebastien Rodriguez of the University of Paris Diderot, in collaboration with Cassini visual and infrared mapping spectrometer team members at the University of Nantes, France. "We see lots of clouds during the summer in the southern hemisphere, and this summer weather seems to last into the early fall. It looks like Indian summer on Earth, even if the mechanisms are radically different on Titan from those on Earth. Titan may then experience a warmer and wetter early autumn than forecasted by the models."

On Earth, abnormally warm, dry weather periods in late autumn occur when low-pressure systems are blocked in the winter hemisphere. By contrast, scientists think the sluggishness of temperature changes at the surface and low atmosphere on Titan may be responsible for its unexpected warm and wet, hence cloudy, late summer.

As summer changes to fall at the equinox in August 2009, Titan's clouds are expected to disappear altogether. But, circulation models of Titan's weather and climate predict that clouds at the southern latitudes don't wait for the equinox and should have already faded out since 2005. However, Cassini was still able to see clouds at these places late in 2007, and some of them are particularly active at mid-latitudes and the equator.

Titan is the only moon in our solar system with a substantial atmosphere, and its climate shares Earth-like characteristics. Titan's dense, nitrogen-methane atmosphere responds much more slowly than Earth's atmosphere, as it receives about 100 times less sunlight because it is 10 times farther from the sun. Seasons on Titan last more than seven Earth years.

Scientists will continue to observe the long-term changes during Cassini's extended mission, which runs until the fall of 2010. Cassini is set to fly by Titan on May 6.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the Cassini-Huygens mission for NASA's Science Mission Directorate. The Cassini orbiter was designed, developed and assembled at JPL. The visual and infrared mapping spectrometer team is based at the University of Arizona.

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